Surgically implantable pumps or valves are used to treat various medical conditions that require long-term delivery of therapeutic drugs such as pain medication, or that require drainage of abnormal fluid accumulation in disorders such as hydrocephalus, a neurological condition in which drainage of cerebrospinal fluid (CSF) from the ventricles, or cavities, of the brain, is blocked in some way. Blockage of this drainage increases pressure on the brain that, left untreated, can result in serious medical conditions including subdural hematoma, compression of the brain tissue, and impaired blood flow.
Hydrocephalus is most often treated by surgically inserting a CSF drainage device, typically called a shunt, to controllably drain excess fluid from a ventricle to another area of the body where it can be absorbed or eliminated. Often the shunt system includes a valve that is noninvasively adjustable through the patient's skin so that a medical practitioner can provide a flow or pressure settings that are appropriate for a patient's condition over time.
It is important for medical practitioners to be able to accurately identify the location of an implanted valve under the patient's skin, to read a setting of the valve, and to adjust the valve's setting. The implanted valve is typically palpatable through the patient's skin and many tools for locating the valve are shaped to complement a physical profile of the valve so that the tool can be positioned and oriented correctly on the patient's skin over the valve, and then held in place for reading and setting the valve using one or more additional tool. Proper positioning of such physical locator tools depends on the valve being reliably palpatable through overlying skin, a characteristic that can be compromised by swelling of tissue near the valve, or by other variations from patient to patient. In addition, application of a conformal locator tool can also be a cause of patient discomfort.
Often, separate tools and complex, time-consuming operational steps are required to perform the locating, reading and setting functions noninvasively. Some types of valves are read using x-ray imaging. Some other valves include a magnetic rotor, an orientation of which can be read using a magnetic compass-like device or one or more magnetic field sensors physically registered to a locator device. Many valves are adjusted using strong magnets applied from outside the body. Commonly, the presence of a strong adjusting magnet prevents the user from reading the valve while setting it.
Accordingly, a need exists for improved tools that enable noninvasively adjustable implanted valves to be located, read and adjusted simply and reliably.